Single ply roof guarantees usually cover 15-20 years, but the actual roof can...

https://www.charliebookmarks.win/single-ply-roof-guarantees-usually-cover-15-20-years-but-the-actual-roof-can-2

Single ply roof guarantees usually cover 15-20 years, but the actual roof can last 25-40 years with proper care. The guarantee protects against faults, not wear and tear or poor maintenance